Warps or sheetlike rolls of threads are prepared by drawing many separate threads from individual packages of thread and winding the threads on a central core, a process known as warping or beaming. These thread packages typically are mounted on a creel, a structure which supports the thread packages while the thread ends are drawn from the thread packages to the warp beam.
Before starting the warp beaming operation, it is necessary to maintain a degree of tension in the threads being drawn from the creel by the warp beaming apparatus. This thread tension prevents adjacent threads from contacting each other and tangling, and promotes even winding of the warp beam. The unwinding friction imparted as the thread is pulled from the thread package, and the air friction acting on the thread while running at high beaming speeds, normally maintain adequate tension in the thread when the warp beaming operation is underway. When the operator is initially drawing the threads from the creel to the warper, and while the warper is running at relatively slow startup speeds, some additional source of thread tension is usually needed to keep the threads from going slack. For this purpose, a thread creel usually includes some kind of thread tensioning or clamping device for each thread package supported by the creel. These thread clamps, frequently located in close proximity to tension monitoring apparatus for the threads, can selectably engage each individual thread being withdrawn from the creel and maintain predetermined tension in the threads on the creel as the warping operation is starting, or while a broken thread end is being repaired. These thread clamping devices also maintain thread tension at the individual yarn packages while the warper is topped, preventing tangling between individual threads.
If a thread breaks or loses adequate tension for any reason, the warping operation will be interrupted while an operator repairs the broken thread or other problem. The tension in each thread being withdrawn from the creel thus must be monitored with some appropriate mechanism or device, because detecting thread breakage by visual inspection is impractical due to the large number of thread packages on a typical creel and the operating speed of the warp beaming apparatus.
Devices for monitoring thread tension and for selectably clamping the thread are known in the art, one such device being disclosed in U.S. Pat. No. 3,873,043. Prior-art thread monitoring and clamping devices in general have been less than satisfactory. Such devices typically include a hook or similar thread-engaging member which retains the running thread in the tension monitoring device, and the device thus defines a twisted or tortuous path for inserting the thread around the tension thread engaging member. While the time or effort required to insert an individual thread into its corresponding tension sensing device may not seem particularly large, a typical creel carries several hundred thread ends which must be individually threaded through a corresponding number of individual tension assemblies. Thus, the cumulative additional time required by the creel operator to individually insert several hundred threads into corresponding tension assemblies becomes a significant factor in the down time of a creel. Furthermore, a thread tension monitoring device having a twisted or other non-straightline path for inserting the thread presents the possibility of misthreading by the operator, in which case even more time is required to correct that mistake.